U.S. troops move into Port-au-Prince, Haiti, to help keep order, distribute aid

This gallery collects all of our photos of the crisis in Haiti, starting with the most recent images and going back to the first photos that emerged after an earthquake hit the impoverished nation Jan. 12.

PORT-AU-PRINCE, HAITI -- Hundreds of U.S. troops surged into the epicenter of Haiti's earthquake-ravaged capital Tuesday to guard convoys and food distribution sites, while thousands more stationed themselves on ships and helicopters offshore to bolster relief and recovery efforts.

One week after a 7.0-magnitude quake crippled this city, many Haitians living on the streets have still not received any food or medical assistance from their government or the international community, but there were increasing signs that the aid effort is gaining momentum.

As the U.N. Security Council approved 3,500 additional peacekeepers for the Haiti mission, the U.S. military and other foreign forces began dropping food from planes, delivering troops by helicopter to volatile neighborhoods, and working to prepare other entry points for aid deliveries.

U.S. Navy divers arrived at Port-au-Prince's crippled port -- where a pier was perilously listing and two of three cranes were submerged -- to help engineers decide how much weight the docks could hold. Slowly, almost gingerly, they began to unload shipping containers from a barge that had sailed from Mobile, Ala., filled with supplies for the World Food Organization and Catholic Relief Services.

"It's really shaky down there," said one of the divers, Chris Lussier.

The delivery of aid was still hampered in some cases, leading to frustration among Haitians and the workers trying to help them. The medical organization Doctors Without Borders said in a statement Tuesday that another one of its cargo planes had been diverted from landing at the Port-au-Prince airport, where officials have struggled to cope with the massive influx of aid. The group said it has had five flights, with a total of 85 tons of medical supplies, refused landing so far.

Army Maj. Gen. Daniel Allyn, second in charge of the U.S. military operation in Haiti, said officials "continue to make progress," but added: "We do not underestimate the scope of the challenge here."

Allyn said troops are working to open more airfields, get more trucks to help deliver water and supplies to victims, and bring in repair and construction equipment to start removing rubble. Some front-loaders could be seen beginning to scoop up the debris of several downtown buildings.

As of Tuesday morning, Allyn said, there were about 2,000 U.S. troops on the ground and about 5,000 on ships or helicopters offshore helping in the efforts. The U.S. military is eventually expected to have 10,000 troops involved in the operation -- with half of them coming ashore.

U.S. and Canadian military forces have been designated to guard food distribution sites as they open, freeing the U.N. security forces to patrol and keep order. The additional U.N. peacekeeping personnel approved Tuesday will bring the total in Haiti to 12,500.

Throughout the morning, U.S. Navy Black Hawk helicopters shuttled in troops from the Army's 82nd Airborne Division to the National Palace compound in the center of the city. The palace itself is in ruins, but the compound is fenced off and the troops appeared to be setting up a temporary camp.

Hundreds of Haitians, many of whom are living in a squalid tent city just outside the palace grounds, pressed against the iron bars to watch the troops arrive. An old man pushed around a wheelbarrow full of popcorn, selling small plastic bags of it.